Cyclic oligomers with repeat units corresponding to condensation polymers such as polyesters and polycarbonates are known. These cyclic oligomers can often be converted to their corresponding linear polymers by ring-opening polymerization. Cyclic oligomers of some aromatic amides have been made.
Cyclic oligomers of (substituted) p-phenylene terephthalamide have been prepared. See, for example, W. Memeger Jr., et al., Macromolecules, vol. 26, p. 3476-3484 (1993) and Polym. Prepr., vol. 34, p. 71-72 (1993). No cyclic meta-substituted aromatic amides are disclosed in this paper.
F. E. Elhadi, et al., Tetrahedron Lett., vol. 21, p. 4215-4218 (1980) reports the synthesis of N-substituted cyclic trimers of m-aminobenzoic acid. Cyclic oligomers of diamines and dicarboxylic acids are not mentioned.
T. L. Guggenheim, et al., Polymer Prepr., vol. 30, p. 138-139 (1989) report the attempted synthesis of the cyclic oligomer of m-phenylene isophthalamide by a high dilution reaction procedure, but they report no "appreciable amount of cyclic formation".
Y. H. Kim, et al., Abstracts of the 35th IUPAC International Symposium on Macromolecules, University of Akron, Jul. 11-15, 1994, report the synthesis of a nitro-substituted cyclic oligomer of m-phenylene isophthalamide. Also reported is a metal salt complex of this cyclic oligomer.